The most desirable minimum was derived s.olely. for the sum- 

 mer irrigation months and assumed to apply to all low water 

 months. This assumption, which may not be valid for the 

 Gallatin River, probably explains the unavailability of the 

 most desirable minimum during the winter period. 



L: 1. 'f-''..l Big Hole River - Reach #1 



Summary flow statistics for a 49-year period of record 

 were derived from data collected at the USGS gage near Mel- 

 rose. Flows at this gage reflect the diversion of water that 

 occurs during the July through October irrigation period. 



During the winter months of December through March when 

 few depletions occur, the absolute minimum recommendation of 

 400 cfs is available in 5 of 10 years and less. This absolute 

 minimum was derived solely for the summer irrigation months 

 and assumed to apply to all low water months. This assump- 

 tion, which may not be valid for the Big Hole River, may 

 partially explain the general unavailability of the absolute 

 minim\mi recommendation during the winter period. . >^ 



During the irrigation months, the availability of water 

 for instream uses appears most limited during September when 

 the absolute minimum recommendation is available in less than 

 4 of 10 years. Additional irrigation depletions above the 

 present level should be curtailed if a desirable fishery is , 

 to be maintained in reach #1. 



Manpower and Cost Evaluations . , 



The man-hours expended and costs of applying the three 

 field methods to the five river reaches are summarized in 

 Tables 2 3 and 24. When computing man-hours and costs for 

 each method, it was assumed no other methods were applied ;, 

 in order to provide a more realistic evaluation. 



The IFG method required the greatest expenditure of 

 time. The total man-hours expended on each of the reaches 

 ranged from 71 to 120 for the IFG method versus 34 to 55 for 

 the multiple transect method and 12 to 20 for the single 

 transect method. Most of the total man-hours for all three 

 field methods was expended on the collection of field data. 



The IFG method was also the costliest of the field 

 methods, requiring from $2,9 81 to $3,265 to apply to each of 

 the reaches. Costs of the multiple transect method per reach 

 ranged from $2,705 to $2,865 and costs of the single transect 

 method ranged from $2,56 3 to $2,610. Much of the total cost 

 of each method is attributable to the initial costs of equip- 

 ment (automatic level, tripod, level rod, canyon lines, and 

 minor field equipment) and training (workshop at Santa Cruz, 

 California). This amounted to $2,465 or more than 75% of - - 

 the total cost of each field method. 



76 



